Expand the role of modified_elements to include explicit restyle hints and damage.

This will take the place of setting IS_DIRTY and HAS_CHANGED.

5 files changed, 93 insertions, 27 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 09061a0932f..a1a8825791f 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -1117,11 +1117,41 @@ impl LayoutThread {
             }
         }
 
-        let modified_elements = document.drain_modified_elements();
+        let restyles = document.drain_pending_restyles();
         if !needs_dirtying {
-            for (el, snapshot) in modified_elements {
-                let hint = rw_data.stylist.compute_restyle_hint(&el, &snapshot, el.get_state());
-                el.note_restyle_hint::<RecalcStyleAndConstructFlows>(hint);
+            for (el, restyle) in restyles {
+                if el.get_data().is_none() {
+                    // If we haven't styled this node yet, we can ignore the restyle.
+                    continue;
+                }
+
+                // Start with the explicit hint, if any.
+                let mut hint = restyle.hint;
+
+                // Expand any snapshots.
+                if let Some(s) = restyle.snapshot {
+                    hint |= rw_data.stylist.compute_restyle_hint(&el, &s, el.get_state());
+                }
+
+                // Apply the cumulative hint.
+                if !hint.is_empty() {
+                    el.note_restyle_hint::<RecalcStyleAndConstructFlows>(hint);
+                }
+
+                // Apply explicit damage, if any.
+                if !restyle.damage.is_empty() {
+                    let mut d = el.mutate_layout_data().unwrap();
+                    d.base.restyle_damage |= restyle.damage;
+                }
+
+                // Propagate the descendant bit up the ancestors.
+                if !hint.is_empty() || !restyle.damage.is_empty() {
+                    let curr = el;
+                    while let Some(curr) = curr.parent_element() {
+                        if curr.has_dirty_descendants() { break }
+                        unsafe { curr.set_dirty_descendants(); }
+                    }
+                }
             }
         }
 
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index b38d5d4ec91..661ecadde9d 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -41,6 +41,7 @@ use dom::bindings::refcounted::{Trusted, TrustedPromise};
 use dom::bindings::reflector::{Reflectable, Reflector};
 use dom::bindings::str::{DOMString, USVString};
 use dom::bindings::utils::WindowProxyHandler;
+use dom::document::PendingRestyle;
 use encoding::types::EncodingRef;
 use euclid::{Matrix2D, Matrix4D, Point2D};
 use euclid::length::Length as EuclidLength;
@@ -348,6 +349,7 @@ no_jsmanaged_fields!(Mime);
 no_jsmanaged_fields!(AttrIdentifier);
 no_jsmanaged_fields!(AttrValue);
 no_jsmanaged_fields!(Snapshot);
+no_jsmanaged_fields!(PendingRestyle);
 no_jsmanaged_fields!(HttpsState);
 no_jsmanaged_fields!(Request);
 no_jsmanaged_fields!(RequestInit);
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 5b1f4cfe404..829b1d98192 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -125,7 +125,8 @@ use std::sync::Arc;
 use std::time::{Duration, Instant};
 use style::attr::AttrValue;
 use style::context::ReflowGoal;
-use style::selector_impl::Snapshot;
+use style::restyle_hints::RestyleHint;
+use style::selector_impl::{RestyleDamage, Snapshot};
 use style::str::{split_html_space_chars, str_join};
 use style::stylesheets::Stylesheet;
 use time;
@@ -158,6 +159,29 @@ struct StylesheetInDocument {
     stylesheet: Arc<Stylesheet>,
 }
 
+#[derive(Debug, HeapSizeOf)]
+pub struct PendingRestyle {
+    /// If this element had a state or attribute change since the last restyle, track
+    /// the original condition of the element.
+    pub snapshot: Option<Snapshot>,
+
+    /// Any explicit restyles hints that have been accumulated for this element.
+    pub hint: RestyleHint,
+
+    /// Any explicit restyles damage that have been accumulated for this element.
+    pub damage: RestyleDamage,
+}
+
+impl PendingRestyle {
+    pub fn new() -> Self {
+        PendingRestyle {
+            snapshot: None,
+            hint: RestyleHint::empty(),
+            damage: RestyleDamage::empty(),
+        }
+    }
+}
+
 // https://dom.spec.whatwg.org/#document
 #[dom_struct]
 pub struct Document {
@@ -234,9 +258,9 @@ pub struct Document {
     /// This field is set to the document itself for inert documents.
     /// https://html.spec.whatwg.org/multipage/#appropriate-template-contents-owner-document
     appropriate_template_contents_owner_document: MutNullableHeap<JS<Document>>,
-    /// For each element that has had a state or attribute change since the last restyle,
-    /// track the original condition of the element.
-    modified_elements: DOMRefCell<HashMap<JS<Element>, Snapshot>>,
+    /// Information on elements needing restyle to ship over to the layout thread when the
+    /// time comes.
+    pending_restyles: DOMRefCell<HashMap<JS<Element>, PendingRestyle>>,
     /// This flag will be true if layout suppressed a reflow attempt that was
     /// needed in order for the page to be painted.
     needs_paint: Cell<bool>,
@@ -410,7 +434,7 @@ impl Document {
             Some(root) => {
                 root.upcast::<Node>().is_dirty() ||
                 root.upcast::<Node>().has_dirty_descendants() ||
-                !self.modified_elements.borrow().is_empty() ||
+                !self.pending_restyles.borrow().is_empty() ||
                 self.needs_paint()
             }
             None => false,
@@ -1708,7 +1732,7 @@ pub enum DocumentSource {
 #[allow(unsafe_code)]
 pub trait LayoutDocumentHelpers {
     unsafe fn is_html_document_for_layout(&self) -> bool;
-    unsafe fn drain_modified_elements(&self) -> Vec<(LayoutJS<Element>, Snapshot)>;
+    unsafe fn drain_pending_restyles(&self) -> Vec<(LayoutJS<Element>, PendingRestyle)>;
     unsafe fn needs_paint_from_layout(&self);
     unsafe fn will_paint(&self);
 }
@@ -1722,8 +1746,8 @@ impl LayoutDocumentHelpers for LayoutJS<Document> {
 
     #[inline]
     #[allow(unrooted_must_root)]
-    unsafe fn drain_modified_elements(&self) -> Vec<(LayoutJS<Element>, Snapshot)> {
-        let mut elements = (*self.unsafe_get()).modified_elements.borrow_mut_for_layout();
+    unsafe fn drain_pending_restyles(&self) -> Vec<(LayoutJS<Element>, PendingRestyle)> {
+        let mut elements = (*self.unsafe_get()).pending_restyles.borrow_mut_for_layout();
         let result = elements.drain().map(|(k, v)| (k.to_layout(), v)).collect();
         result
     }
@@ -1830,7 +1854,7 @@ impl Document {
             reflow_timeout: Cell::new(None),
             base_element: Default::default(),
             appropriate_template_contents_owner_document: Default::default(),
-            modified_elements: DOMRefCell::new(HashMap::new()),
+            pending_restyles: DOMRefCell::new(HashMap::new()),
             needs_paint: Cell::new(false),
             active_touch_points: DOMRefCell::new(Vec::new()),
             dom_loading: Cell::new(Default::default()),
@@ -1966,23 +1990,28 @@ impl Document {
         self.id_map.borrow().get(&id).map(|ref elements| Root::from_ref(&*(*elements)[0]))
     }
 
+    fn ensure_pending_restyle(&self, el: &Element) -> RefMut<PendingRestyle> {
+        let map = self.pending_restyles.borrow_mut();
+        RefMut::map(map, |m| m.entry(JS::from_ref(el)).or_insert_with(PendingRestyle::new))
+    }
+
+    fn ensure_snapshot(&self, el: &Element) -> RefMut<Snapshot> {
+        let mut entry = self.ensure_pending_restyle(el);
+        if entry.snapshot.is_none() {
+            entry.snapshot = Some(Snapshot::new(el.html_element_in_html_document()));
+        }
+        RefMut::map(entry, |e| e.snapshot.as_mut().unwrap())
+    }
+
     pub fn element_state_will_change(&self, el: &Element) {
-        let mut map = self.modified_elements.borrow_mut();
-        let snapshot = map.entry(JS::from_ref(el))
-                          .or_insert_with(|| {
-                              Snapshot::new(el.html_element_in_html_document())
-                          });
+        let mut snapshot = self.ensure_snapshot(el);
         if snapshot.state.is_none() {
             snapshot.state = Some(el.state());
         }
     }
 
     pub fn element_attr_will_change(&self, el: &Element) {
-        let mut map = self.modified_elements.borrow_mut();
-        let mut snapshot = map.entry(JS::from_ref(el))
-                              .or_insert_with(|| {
-                                  Snapshot::new(el.html_element_in_html_document())
-                              });
+        let mut snapshot = self.ensure_snapshot(el);
         if snapshot.attrs.is_none() {
             let attrs = el.attrs()
                           .iter()
diff --git a/components/script/layout_wrapper.rs b/components/script/layout_wrapper.rs
index fb31965d45d..3d61a810111 100644
--- a/components/script/layout_wrapper.rs
+++ b/components/script/layout_wrapper.rs
@@ -34,7 +34,7 @@ use dom::bindings::inheritance::{CharacterDataTypeId, ElementTypeId};
 use dom::bindings::inheritance::{HTMLElementTypeId, NodeTypeId};
 use dom::bindings::js::LayoutJS;
 use dom::characterdata::LayoutCharacterDataHelpers;
-use dom::document::{Document, LayoutDocumentHelpers};
+use dom::document::{Document, LayoutDocumentHelpers, PendingRestyle};
 use dom::element::{Element, LayoutElementHelpers, RawLayoutElementHelpers};
 use dom::node::{CAN_BE_FRAGMENTED, DIRTY_ON_VIEWPORT_SIZE_CHANGE, HAS_CHANGED, HAS_DIRTY_DESCENDANTS, IS_DIRTY};
 use dom::node::{LayoutNodeHelpers, Node};
@@ -65,7 +65,7 @@ use style::dom::{LayoutIterator, NodeInfo, OpaqueNode, PresentationalHintsSynthe
 use style::dom::{TRestyleDamage, UnsafeNode};
 use style::element_state::*;
 use style::properties::{ComputedValues, PropertyDeclarationBlock};
-use style::selector_impl::{NonTSPseudoClass, PseudoElement, RestyleDamage, ServoSelectorImpl, Snapshot};
+use style::selector_impl::{NonTSPseudoClass, PseudoElement, RestyleDamage, ServoSelectorImpl};
 use style::selector_matching::ApplicableDeclarationBlock;
 use style::sink::Push;
 use style::str::is_whitespace;
@@ -377,8 +377,8 @@ impl<'ld> ServoLayoutDocument<'ld> {
         self.as_node().children().find(ServoLayoutNode::is_element)
     }
 
-    pub fn drain_modified_elements(&self) -> Vec<(ServoLayoutElement<'ld>, Snapshot)> {
-        let elements =  unsafe { self.document.drain_modified_elements() };
+    pub fn drain_pending_restyles(&self) -> Vec<(ServoLayoutElement<'ld>, PendingRestyle)> {
+        let elements =  unsafe { self.document.drain_pending_restyles() };
         elements.into_iter().map(|(el, snapshot)| (ServoLayoutElement::from_layout_js(el), snapshot)).collect()
     }
 
diff --git a/components/style/servo/restyle_damage.rs b/components/style/servo/restyle_damage.rs
index 616c3506173..6cabb7eb485 100644
--- a/components/style/servo/restyle_damage.rs
+++ b/components/style/servo/restyle_damage.rs
@@ -4,6 +4,7 @@
 
 use computed_values::display;
 use dom::TRestyleDamage;
+use heapsize::HeapSizeOf;
 use properties::ServoComputedValues;
 use std::fmt;
 use std::sync::Arc;
@@ -48,6 +49,10 @@ bitflags! {
     }
 }
 
+impl HeapSizeOf for ServoRestyleDamage {
+    fn heap_size_of_children(&self) -> usize { 0 }
+}
+
 impl TRestyleDamage for ServoRestyleDamage {
     /// For Servo the style source is always the computed values.
     type PreExistingComputedValues = Arc<ServoComputedValues>;